The width, measured in pixels, of the bars of a bar-chart-view in a chart-widget. The value should be a positive
integer. The default value is 12.

When there are multiple side-by-side bars for each chart item (which
is when there are multiple chart-objects and the values-are-stacked property
is nil), this is the width of a single bar
rather than the width of the group of side-by-side bars.

If fit-chart-items is true,
then this value will be scaled proportionally with other sizing
properties to make all data fit in view.